XB-ART-4997
J Mol Biol
2003 Jul 25;3305:1203-13. doi: 10.1016/s0022-2836(03)00656-9.
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Probing the sensory rhodopsin II binding domain of its cognate transducer by calorimetry and electrophysiology.
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Sensory rhodopsin II, a repellent phototaxis receptor from Natronobacterium pharaonis (NpSRII) forms a tight complex with its cognate transducer (NpHtrII). Light excitation of the receptor triggers conformational changes in both proteins, thereby activating the cellular two-component signalling cascade. In membranes, the two proteins form a 2:2 complex, which dissociates to a 1:1 heterodimer in micelles. Complexed to the transducer sensory rhodopsin II is no longer capable of light-driven proton pumping. In order to elucidate the dimerisation and the size of the receptor-binding domain of the transducer, isothermal titration calorimetry and electrophysiological experiments have been carried out. It is shown, that an N-terminal sequence of 114 amino acid residues is sufficient for tight binding (K(d)=240nM; DeltaH=-17.6kJmol(-1)) and for inhibiting the proton transfer. These data and results obtained from selected site-directed mutants indicate a synergistic interplay of transducer transmembrane domain (1-82) and cytoplasmic peptide (83-114) leading to an optimal and specific interaction between receptor and transducer.
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Species referenced: Xenopus
Genes referenced: rho